In packaging agricultural fibrous crops, such as hay and straw, as well as in industrial packaging, strings or twines are often used to hold loose fibrous substances together for handling and transportion. In some applications, especially in agriculture the use of clamps to secure the strings around bales is undesirable, therefore, the ends of the strings forming the loops around bales are knotted together. There are several models of knotting devices, all of them applying the same basic process, by forming a loop of the string around a properly designed functional element, generally known in the industry as a "bill hook", and feeding the string through the loop to form a self-locking knot, which while being pulled off the bill hook becomes tight thereby securing the string around the package in a closed loop.
This knotting process requires a relatively complex mechanism with close manufacturing and operating tolerances, and calls for maintaining proper tension in the strings during the knot forming process. Excessive tension in the strings can result in making the knot too tight around the bill hook preventing its removal, thereby causing tying failure. Excessively loose strings may prevent their proper positioning for interaction with the operating components of the knotter. A rough or corroded surface on the bill hook also can effect the removal of the knot. Even air humidity can lead to problems by effecting the frictional relationships between the string and the bill hook. One of the principal shortcomings of this knotting process is that after the removal of the knot from the bill hook slack remains in the looped string around the package allowing the packaged substance to expand. This expansion reduces the density of the package that was achieved in the densification process. In order to maintain a desired final density the actual compressed density has to be higher, requiring additional energy input, causing increased stress in the apparatus. The expansion of the bale also can cause undesirable changes in its final shape.
It is, therefore, necessary to make improvements in the process of securing strings around such packages.
My invention applies a unique method that requires a simple mechanism, not calling for close operating tolerances, not being sensitive to the tension in the string, forming the self-locking knot directly on the string and not on any component of the mechanism, and making tightly wrapped loops around the bales or packages.